Structural members are available in a wide variety of configurations to provide structural support under a variety of loading conditions. In particular, the wing and empennage surfaces of an aircraft typically include parallel and span-wise oriented structural members called stringers that are coupled to skin members on the wing and empennage surfaces that cooperatively provide the desired flexural and torsional stiffness to the wing and empennage surfaces. Typically, the wing and empennage surfaces are fabricated from a metal, such as aluminum, steel or titanium, and the stringer includes a planar web portion that is generally oriented in a direction approximately perpendicular to the skin member and extending in a span wise direction along the wing or empennage surface so that the web portion offers resistance to a bending moment generated by the load. A flange portion may be positioned on one or both of the longitudinal edges of the web portion in order to provide resistance to localized failure of the web portion due to lateral buckling. The flange portion further allows the stringer to be coupled to the skin member by providing an attachment surface for the skin member.
Reinforced polymer-based materials are also available that may be used to form various structural members, and may be used as a substitute for metals, particularly in applications where relatively low weight and high mechanical strength is desired. As a result, reinforced polymer-based materials are widely used in a variety of commercial and military aircraft, terrestrial vehicles and consumer products. The material is generally comprised of a network of reinforcing fibers that are generally applied in layers, and a polymeric resin that substantially wets the reinforcing fibers to form an intimate contact between the resin and the reinforcing fibers. The material may then be formed into a structural component by a variety of known forming methods, such as an extrusion process or other forming processes.
Although desirable results have been achieved using prior art apparatus and methods, a stringer and skin structure that may be more easily and inexpensively fabricated, and that may provide a more favorable strength to weight ratio in comparison to conventional stringer and skin structures, would have utility.